Regenerator seal support



United States Patent Inventor Hugh C. Carroll LockporLNewYork Appl. No.774,332 Filed Nov. 8, 1968 Patented Oct. 20, 1970 Assignee GeneralMotors Corporation Detroit, Michigan in corporation of DelawareREGENERATOR SEAL SUPPORT 3 Claims, 5 Drawing Figs.

US. Cl. 165/9, 277/96 Int. Cl ..F28d 19/04, F16j 15/54 Field of Search165/9; 277/92 References Cited UNITED STATES PATENTS 3,234,999 2/1966Atwood 165/9 9/ 1966 Chapman et al ABSTRACT: An axial-flow rotaryregenerator has fluid seals which extend between the fixed housing ofthe regenerator and the matrix and define the perimeters 0f the fluidflow paths. The seals can yield to distortions of the matrix or housing. Each seal includes a matrix-engaging element, a flexible sealingmembrane engaging the housing and welded to the matrix-engaging element,a supporting membrane disposed on the low pressure side of the sealingmembrane, and a support plate disposed on the low pressure side of thesupporting membrane. The support plate has a hinged connection to thematrix-engaging element through an abutment strip welded to thematrix-engaging element. The support plate is a zigzag strip formed byrolling a corrugated sheet so as to collapse the corrugations together.

HIGHER PRESSURE /fi2 Q, #1

LOWER PRESSURE Patented Oct. 20, 1970 I N VEN TOR. fiayi E far/0% B Y\glHGHER PRESSURE REGENERATOR SEAL SUPPORT My invention relates toimprovements in sealing arrangements for rotary regenerators,particularly those of the axialflow type. Such regenerators are devicesin which a finely porous metal or ceramic disk is slowly rotated so thateach element of the disk passes successively through two gas paths,absorbing heat from the hotter gas and releasing it to the cooler gas.

One application of such regenerators is in preheating the combustion airin gas turbine engines. in this case, there is a large pressuredifference between the compressedair which is heated and the turbineexhaust gases which give up heat. in order to prevent leakage of thehigh pressure fluid into the low pressure fluid path and also to preventeach fluidfrom bypassing the matrix, seals are provided which extendaround the perimeter of one or both flow paths on each face of theregenerator, bridging the gap between the regenerator disk and a face ofthe enclosing housing which is proximate to the matrix. Particularlywith metal matrices, sealing problems are aggravated by distortion ofthe matrix due to the large temperature gradient between the two faces.

Because of the relative warping of the matrix and and the housing andbecause of the very high temperatures of the regenerator when employedwith gas turbines, provision of an adequate, durable, and economicallypracticable seal has presented difficult problems. The purpose of myinvention is to provide a seal between a rotary regenerator matrix andthe matrix housing which is exceptionally effective, is durable andreliable, and which can be fabricated at a reasonable cost.

The principal objects of my invention are to advance the art of rotaryregenerators, to make such regenerators commercially feasible forapplications such as gas turbine engines, and to provide an improvedseal for a rotary regenerator. A further object is to provide a simpleseal having a minimum of leakage paths. A further object is to providean economical support for a flexible seal having superiorcharacteristics. I

The nature of my invention and its advantages willbe clear to thoseskilled in the art from the succeeding detailed description of thepreferred embodiment of the invention and the accompanying drawingsthereof.

FIG. 1 is a schematic view of a rotary regenerator taken in a planecontaining the axis of rotation of the matrix.

FIG. 2 is a sectional view of a regenerator embodying my improved sealtaken on a plane perpendicular to the axis of rotation as indicated bythe line 2-2 in FIG. 1.

FIG. 3 is an enlarged view of a portion of the seal as illus trated inFIG. 2.

FIG. 4 is a still further enlarged cross-sectional view taken on theplane indicated by the line 4-4 in FIG. 3.

FIG. 5 is an enlarged sectional view taken on the plane indicated by theline 5-5 in FIG. 2.

Before proceeding to the detailed description, it may be mentioned thatmy invention is described as embodied in an axial-flow regenerator ofthe type to which Chapman et al. U.S. Pat. No. 3,273,903 for RegeneratorSeal for a Gas Turbine Engine, Sept. 20, 1966, Bracken et al. U.S. Pat.No. 3,368,611 for Rotary Regenerator Seal with High Pressure FluidRecovery, Feb. 13, 1968, and Bracken et al. U.S. Pat. No. 3,476,173 forRotary Regenerator Matrix Mount and Drive are directed. The particularseal structure is a modification of that described in U.S. Pat.application Ser. No.

r 769,928 filed Oct. 23, 1968 of Joseph. W. Bracken, Jr. for

Regenerator Seal, of common ownership.

Referring first to FIG. 1, the regenerator comprises a housing which isgenerally drum-shaped and which encloses an annular matrix 11 which isof a structure defining pores or passages 12 (greatly enlarged inFIG. 1) extending from face to face of the matrix generally parallel tothe axis of rotation defined by a matrix locating and driving shaft 13.Shaft 13 is mounted in suitable bearings in a boss 15 on the housing andterminates in a spider 17 which is coupled to the matrix by means (notillustrated, which may be of the type described in the abovementionedU.S. Pat. No. 3,476,173) so that the matrix may be rotated slowly. Thematrix preferably includes a nonporous inner rim l8 and an outernonporous rim l9. It is not essential that such rims be provided,however. A generally cylindrical space 21 is defined within-the interiorof the matrix and a space 22 extends around the periphery of the matrixwithin the housing 10. An inlet 23 for cool high pressure air enters oneface of the housing and opposite to it an outlet 25 is provided for theheated compressed air. The hot low pressure exhaust gases enter throughan inlet 26 and leave the regenerator through an outlet 27, the twostreams being thus in counterflow relation, althoughfth'isis notessential to the invention. Also, the hot gas passage is of larger areathan the cold air passage because of the difference in density, but thisalso is merely incidental to the invention.

A sealing means or seal assembly 28 is provided. between each face ofthe matrix and the housing to confine the cold and hot gases to thedesired paths through-the matrix from inlet to outlet and minimizeleakage between. the paths. As shown more clearly in FIG. 2, such a sealcomprises two arms 30 and 31 extending radially of the matrix facepreferably joined at the center of the matrix and joined at the outerrim of the matrix by an arcuate rim or by-pass seal 34 extending aroundthe high pressure path and an arcuate rim seal 35 extending around thelow pressure path. The seal assembly thus defines an opening 37 for theheated high pressure air and an opening 38 for the hot low pressureexhaust gases, these openings as shown in FIG. 2 conforming generally tothe outline of the ducts 25 and 26. v

The seal arms 30 and 31 together may be termed a cross arm seal, thislying between the high pressure and'low pressure fluid paths and theseal portions 34 and 35 may be termed a rim seal or bypass seal, thesebeing engaged with the matrix adjacent its periphery. The rim sealportion 34 and the cross arm seal surround the high pressure passage andthe cross arm seal and rim seal portion 35 surround the low pressure gaspassage. It is common practice for the high pressure air to occupy thespace 22 radially outward of the matrix, in which case the rim sealportion 34 may be omitted at the entrance 23 to the matrix.

Proceeding now to FIGS. 2 to 5 for a detailed description of preferredstructure of the sealing means, these figures are views of the seal atthe outlet side of the air path and the inlet side of the gas path. Theprincipal structural element of the seal is a carrier or frame 40 which,in this particular seal, consists of a circular portion forming part ofthe rim seals 34 and 35 and an angular cross arm portion extendingthrough the cross arm seal portions 30 and 31. Preferably, this is aunitary structure of rather heavy sheet metal so that it is rigid in thedirection perpendicular to the axis of rotation of the matrix but iscapable of flexing to a certain extent in a direction parallel to theaxis of the matrix. In the particular example described here in whichtheseal is approximately two feet in overall diameter, the carrier 40 isabout 0.06 inch thick. This frame 40 is located positively againstrotation and translatory movement transverse to the axis of rotation,but is free to move parallel to the axis of rotation of the matrix. Thismounting is provided by a number of pins or dowels 41 projecting fromthe fixed structure of the housing 10 into slots in lugs 43 extendingfrom the frame 40. The slots 42 are elongated to provide for relativeradial expansion of the carrier 40 and the regenerator housing 10.

The carrier 40 bears a wear element 45 which is in actual contact withthe matrix throughout the circumference of the rim seals and along thelength of the cross arm seals. The wear element is composed of amaterial or materials suited to the requirements of the installation. Itmay be, for example, a graphite composition or a nickel alloy. The wearelement may be attached in any desired manner to the face of the carrieras by brazing, riveting, or other fastening means. The wear element alsomay be about 0.06 inch thick in the described embodiment. The carrierand the wear element together may be called a matrix-engaging strip orelement 44.

The structure to which my invention is particularly directed lies in themeans for bridging the gap 46 between the carrier 40 and a plane face 48of the housing which underlies the strip 44. Because of the dishing orother distortion and expansion of the matrix as it heats up and possibledistortions and expansion of the case, the width of gap 46 varies notonly with operating conditions of the regenerator but also varies fromone area to another along the strip 44. The problem is, therefore, toprovide a high temperature resistant seal which adapts itself tovariation in the width of the gap 46 and substantially entirely preventsleakage from the higher pressure to the lower pressure through the gap46.

The structure provided for this purpose, shown most clearly in FIGS. 3,4, and 5, embodies four elements comprising a seal disposed between thecarrier or frame 40 and the housing surface 48 and bridging the gap 46.These parts of the seal, in order from the carrier 40, are a sealingmembrane 49, a supporting membrane 50, a support plate 52, and a hingeelement or abutment strip 53. Parts 53, 50, and 49 are all weldedtogether and to the carrier 40 by a row of spot welds or a seam weld or,if desired, attached by mutual brazing along the portion or line 54where all of these pans are stacked together adjacent one edge ofcarrier 40. This weld or other joint is such as to provide a leak-tightconnection between the sealing membrane 49 and the frame. The free edgeof the sealing membrane 49 bears against the face 48 of the housingunder the influence of the differential of gas pressures. As indicatedin H6. 5, the higher pressure is underneath or to the left of thesealing membrane and the lower pressure above or to the right of themembrane. The membrane 49 is of very thin sheet metal so that it isreadily deflected by the pressure into close substantially leak-proofsealing engagement with the surface 48. In the particular example, thisis of 0.002 inch shim stock. Since such very light weight and flexiblematerial could not act as a piston or diaphragm to withstand the forceexerted by the gas pressure differential, the parts 50 and 52 reinforceit and provide the necessary stifiness except at the free edge where theseal is maintained. However, it is necessary that the stiffeningstructure not unduly resist gradual change in width of the gap 46 fromone area of the matrix to another because of torsional stiffness of thesupport plate.

In the seal of the Bracken U.S. Pat. application Ser. No. 769,928referred to above, the support plate is slotted to reduce its torsionalstiffness. According to my invention, the support plate is a strip madeof relatively thin sheet metal in the fonn of overlapping recumbentcorrugations, with the corrugations extending in the direction from edgeto edge of the strip. Because the metal is thin, there is littletorsional stiffness; but because of multiple overlapping, there issufficient beam strength to resist the gas pressure across the span fromedge to edge of the strip.

The preferred form of the corrugations of the support plate 52 isclearly shown in FIG. 4. Deep corrugations are rolled so as to fold themover against each other in a recumbent or leaning relation to provide areadily twisted zigzag strip. in the illustrated example, the materialfrom which plate 52 is formed is about 0.005 inch thick; the overallthickness of the plate is about 0.040 inch.

Notches 56 are cut in the outer edge of plate 52 to vent gas passing thesealing membrane 49 and maintain full pressure differential across themembrane.

One edge of the support plate 52 bears against a flange 58 of the hingeelement 53 so that the support plate is free to swing about itsright-hand edge, as illustrated in FIG. 5, to accommodate variations inwidth of gap 46. The flange 58 is broken by closely spaced slots 59 sothat it does not unduly stiffen the carrier 40 and thus lessen theability of the carrier to accommodate to the curvature of the matrix.

The supporting membrane .50 serves two functions; it bridges theunevennesses in the'surface of the stipportplate to prevent undue localloading and wear of the sealing membnane 49 while maintaining theflexibility of the support plate 52. Also, it serves to retain thesupport plate in position against the hinge element 53. In the partlcuar example, this membrane is 0.004 inch thick. As shown clearly in FIGS.3 and 5, the outer edge of the supporting membrane 50 is slotted in linewith thenotches 56 to provide tabs 60 which are doubled back over theouter edge of the support plate 52 and are welded 0r brazed to it.Leakage gas can flow to notches 56 between these tabs. Note that thisouter edge of plate 52 is tapered or feathered, by sanding or otherwise,to a relatively thin edge so that the sealing membrane 49 is supporteddown to a point closely adjacent to the surface 48. As will be seen, thestructure illustrated provides a seal between the strip 44 and thehousing which has but one leakage path. that being at the free edge ofthe sealing membrane 49, and which has structure of great simplicity.

As indicated in FIG. 2. where the cross arm seal joins'the rim seal theportions or parts 49, 50, 52, and 53 are mitered so as to provide asuitable corner joint. A similar miter is proviiied at the angle betweenthe cross arm seal portions 30 and 3 It will be apparent to thoseskilled in the art that the preferred structure described provides asealing structure for a rotary regenerator having superior simplicity, aminimum of leakage, and, in general, a structure of great practicalityand usefulness.

The detailed description of the preferred embodiment of the inventionfor the purpose of explaining the principles thereof is not to beconsidered as limiting or restricting the invention, since manymodifications may be made by the exercise of skill in the art withoutdeparting from the scope of the invention.

lclaim:

1. In a rotary regenerator including a housing and a heattransfer matrixrotatable in the housing about an axis, the matrix and a face of thehousing defining a gap between them the gap being variable in operationof the regenerator, sealing means bridging the said gap obliquelyadaptable to variation of the gap comprising, in combination, amatrix-engaging strip having a rear face confronting the housing face,plate means hinged to the strip bridging the gap between the said faces.the plate means being torsionally yieldable to accommodate convergenceof the gap along the strip, and a thin flexible sealing membranesupported by the plate means across the gap and having edges extendingbeyond the plate means into flexural sealing engagement with the saidfaces, the sealing means being so disposed that the pressuredifferential across the sealing means biases the membrane toward theplate means, the plate means being defined by corrugated sheet metalwith the corrugations extending in the direction across the gap, thecorrugations being deep and recumbent and overlapping to provide aplurality of layers of the sheet metal for sufficient beam strengthacross the gap.

2. A structure as defined in claim 1 including also a flexiblesupporting membrane disposed between the sealing mem brane and the platemeans bridging the corrugations in the plate means.

3. A structure as defined in claim 2 in which the supporting membrane isfixed to the strip and plate means and retains the plate means on thestrip.

